1. Field of the Invention
The present invention relates to a knockout device which serves to knock out a work plate such as a printed board and the likes after a punching for the work plate is completed in a press-machine such as a mechanical press and an oil hydraulic press, etc.
2. Prior Art
As a technology to be premised for such a knockout device, have so far been known ones disclosed in Japanese utility model publication No. 32916 of 1985 (referred to as first conventional embodiment hereinafter) and in Japanese utility model publication No. 34426 of 1985 (referred to as second conventional embodiment hereinafter). These first and second conventional embodiments have the nearly same basic constructions as that of the present invention.
Now the basic construction will be explained with reference to FIGS. 5 and 6 showing the first conventional embodiment and to FIG. 7 showing the second conventional embodiment hereinafter.
By the way, the component parts having the same functions in the first and the second conventional embodiments are indicated by the same symbols in common.
That is, in a knockout device, there are provided a plurality of punches 113 fixedly secured to the underside of a base plate 108 through a punch fixation plate 109 and a punch support plate 110 so as to protrude downwardly. A work fixation plate 114 is fitted to the punches 113 vertically slidably. A cylinder chamber 120 of an oil hydraulic knockout cylinder 119 is formed in the upper portion of the base plate 108 and an actuation-plate guide hole 121 is formed in the lower portion thereof. A piston 122 is provided vertically slidably in the cylinder chamber 120, and a knockout actuation-plate 123 is provided vertically slidably n the guide hole 121. A plurality of knockout pins 124 are provided so as to pass vertically slidably through both the punch fixation plate 109 and the punch support plate 110, and the work fixation plate 114 is adapted to be actuated downwardly by the downward movement of the piston 122 through the knockout actuation-plate 123 and the knockout pins 124 so as to knock out downwardly the punched work plate frictionally engaged with the punches 113.
The knockout device having this basic construction, for example as shown in FIG. 5, is fixedly secured to the slide 103 of the press-machine 101 so as to be driven vertically and integratedly therewith 103.
When the slide 103 is moved to the top dead center in the vertical movement thereof, the cylinder chamber 120 is adapted to be pre-pressurized by a cushion pressure oil supplied from an oil hydraulic control device (but not shown in Figs.) so that the work fixation plate 114 is pushed to a lower position than that of the punches 113 through both the knockout actuation-plate 123 and the knockout pins 124.
During the descendant actuation stroke to perform a punching work, first of all the work fixation plate 114 abuts onto the work plate 106 so as to fix it by the cushion pressure in the cylinder chamber 120. And then the punches 113 continue to descend and protrude toward the lower side of the work fixation plate 114 so that the work plate 106 is punched thereby.
When the slide 103 reaches the bottom dead center, the work plate 106 tends to frictionally engage with the punches 113 after the completion of punching.
During the ascendant restoration stroke for the knockout operation, the work plate 106 is raised by the punches 113 in a frictional engagement therewith and then it is separated from the punches 113 by the knockout operation of the work fixation plate 114 which is moved downwardly through the knockout pins 124 by the knockout oil pressure supplied to the cylinder chamber 120 by the oil hydraulic control device.
After that, the pressure in the cylinder chamber 120 is reduced to the value of the cushion oil pressure, the slide 103 returns to the top dead center thereof again, and one cycle of the punching work is completed.
In the above-mentioned knockout device, in case that the knockout actuation-plate 123 inclines, the work fixation plate 114 is also inclined through the knockout pins 124, and then the punches 113 are subjected to a bending to cause some offsets relative to the punch holes 104a provided in the lower die 104. Therefore, the punches 113 and the punch holes 104a are apt to suffer abnormal abrasions and breakages.
In order to solve these problems, there is provided a means for guiding the knockout actuation-plate 123 vertically linearly in the base plate 108. As shown in FIG. 6 the guide ratio tan .theta.[=guide height(h.sub.2)/guide width(l.sub.2)] is set to a constant value.
In the basic construction, the linear guide construction for the knockout actuation-plate 123 is constructed as follows in a prior art.